Semiconductor devices for detecting the physical quantity distribution in which a plurality of unit elements (for example, pixels) responsive to electromagnetic waves, such as light or radiation, input from an external source, are disposed in a line or a matrix are used in various fields.
In the video equipment field, CCD (Charge Coupled Device), MOS (Metal Oxide Semiconductor), or CMOS (Complementary Metal-oxide Semiconductor) solid state imaging devices for detecting light (an example of electromagnetic waves) as the physical quantity are used. Such imaging apparatuses read the physical quantity distribution obtained by converting light into an electric signal by using the unit elements (pixels in the solid state imaging devices) as the electric signal.
Solid state imaging devices include amplifying solid state imaging devices. Amplifying solid state imaging devices have pixels formed of amplifying solid-state imaging devices (APS; Active Pixel Sensors/also referred to as “gain cells”) having amplifying driving transistors in pixel signal generators for generating pixel signals according to signal charge generated in charge generators. For example, many CMOS solid state imaging devices have such a configuration.
In this type of amplifying solid state imaging device, to read out pixel signals to an external source, address control is performed on a pixel portion in which a plurality of unit pixels are disposed so that the signals are selectively read from the individual unit pixels. That is, the amplifying solid state imaging device is an example of an address-control solid state imaging device.
For example, in an amplifying solid-state imaging device, which is one type of X-Y address solid-state imaging device having unit pixels disposed in a matrix, MOS-structured active devices (MOS transistors) are used for forming the pixels so that the pixels themselves have an amplifying function. That is, signal charge (photoelectrons) stored in photodiodes, which are photoelectric conversion devices, is amplified by the active devices and the amplified signal charge is read as image information.
In this type of X-Y address solid-state imaging device, for example, many pixel transistors are disposed in a two-dimensional matrix to form a pixel portion, the accumulation of signal charge in accordance with incident light in each line (row) or each pixel is started, and current or voltage signals based on the accumulated signal charge are sequentially read from the individual pixels by addressing. In MOS (including CMOS) solid-state imaging devices, an address control method for accessing the pixels in one row at one time and reading the pixel signals from the pixel portion in units of rows is mostly used.
The analog pixel signal read from the pixel portion is converted into digital data in an analog-to-digital converter (AD converter) if necessary. Accordingly, various AD conversion mechanisms have been proposed (for example, see References 1 to 6, below). In some of the known publications, in accordance with the method for accessing the pixels in one row at one time and reading the pixel signals from the pixel portion, a so-called column parallel system in which an AD converter and a signal processor for performing signal processing other than AD conversion are disposed for each vertical column is employed.    REFERENCE 1—W. Yang et al., “An Integrated 800×600 CMOS Image System”, ISSCC Digest of Technical Papers, pp. 304-305, February, 1999    REFERENCE 2—Kazuya Yonemoto, “CCD/CMOS Sensor no Kiso to Ohyo” (“Basic and Applied CCD/CMOS Sensor”, CQ Publishing Co., Ltd., Aug. 10, 2003, the first edition p 201-203    REFERENCE 3—Toshifumi Imamura, Yoshiko Yamamoto, “3. Kosoku/Kino CMOS Image Sensor no Kenkyu” (“Research on Fast/Functional CMOS Image Sensor”, [online], [searched on Mar. 15, 2004], the Internet <URL:http://www.sankaken.gr.jp/project/iwataPJ/report/h12/h12index.html>    REFERENCE 4—Toshifumi Imamura, Yoshiko Yamamoto, Naoya Hasegawa, “3. Kosoku/Kino CMOS Image Sensor no Kenkyu” (“Research on Fast/Functional CMOS Image Sensor”, [online], [searched on Mar. 15, 2004], the Internet <URL:http://www.sankaken.gr.jp/project/iwataPJ/report/h14/h14index.html>    REFERENCE 5—Oh-Bong Kwon et al., “A Novel Double Slope Analog-to-Digital Converter for a High-Quality 640×480 CMOS Imaging System”, VL3-03 1999 IEEE p 335-338    REFERENCE 6—Japanese Unexamined Patent Application Publication No. 11-331883    REFERENCE 7—Japanese Unexamined Patent Application Publication No. 2001-268451
Various types of processing are executed on pixel signals output from the pixels to generate high-quality images or to use the pixel signals for special applications. For example, References 4 and 5 referred to above disclose the following mechanism for detecting edges. Currents from a plurality of pixels for detecting light are simultaneously output to an output bus and are added or subtracted on the output bus. Then, the resulting currents are converted into pulse width signals having a magnitude in the time axis, and the pulse width signals are AD-converted by counting the numbers of clocks of the pulse widths of the pulse width signals in counter circuits disposed vertically in parallel with each other, thereby converting the addition/subtraction result into digital data.
Reference 7 referred to above discloses a mechanism for detecting a moving part by generating the difference between pixel signals obtained at different time points in an analog area and by converting the difference into digital data (for example, binary values).
Reference 8 below discloses the following mechanism. By using the capacity within a pixel as an inter-pixel memory, signal charge detected by a photodiode is temporarily stored in the inter-pixel memory and is then read, thereby implementing an electronic shutter. Reference 9 below discloses the following mechanism. By using the capacity within a pixel as the inter-pixel memory, the previous frame signal is stored and is added to the current frame signal in the pixel, thereby increasing the dynamic range, performing edge processing, or detecting a moving part.    REFERENCE 8—Chye Huat Aw, Bruce A. Wooley, “FA11, 2: A 128×128 Pixel Standard-CMOS Image Sensor with Electronic Shutter”, ISSCC96/SESSION11/ELECTRONIC IMAGING CIRCUITS/PAPER FA11.2, 1996 ISSCC Digest of Technical Papers, pp 180-182    REFERENCE 9—Yoshinori Muramatsu et al., “A signal-Processing CMOS Image Sensor Using a Simple Analog Operation”, IEEE JOURNAL OF SOLID-STATE CIRCUITS, VOL. 38, NO. 1, JANUARY 2003
As disclosed in References 4-5 and 7-9 above, in the arrangement of circuits for performing the above-described types of processing, a processing function for performing various types of processing, such as an addition/subtraction function, is disposed on the image sensor (such a technique is referred to as the “on-chip method”). In particular, it is considered that a so-called “column parallel system” structure in which a signal processor is disposed in each vertical column for reading pixel signals from the pixel portion is suitable for the on-chip method.
In the known mechanisms for performing the above-described processing, only the computed signals are output from the solid state imaging device, and thus, video signals that should be output from the solid state imaging device cannot be obtained together with the computed signals.
As a mechanism for solving this problem, for example, Reference 10 below discloses a motion detecting solid state imaging device in which a structure for detecting only a moving part of a subject is disposed in the solid state imaging device and a signal representing the moving part and the corresponding video signal can be simultaneously output.    REFERENCE 10—Japanese Unexamined Patent Application Publication No. 11-8805
However, in the mechanism disclosed in Reference 3 identified above, when outputting the signal representing the moving part to the outside the solid state imaging device, it is necessary that the signal be subjected to time difference processing before being converted into digital data, and thus, both the time difference processing function in the analog area and the AD conversion function of converting the analog-processed signal into digital data are required.
Additionally, in the mechanism disclosed in Reference 10 identified above, when converting the time-difference-processed signal is converted into digital data, it is converted into binary data. Thus, when conducting adaptive processing outside the solid state imaging device, the flexibility to handle the data is lower than that to handle data in multi levels.